<!DOCTYPE html>
<html lang="zh-CN">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>经典 Header + Sidebar + Content 布局</title>
  <style>
    * {
      margin: 0;
      padding: 0;
      box-sizing: border-box;
    }

    body {
      font-family: Arial, sans-serif;
      background: linear-gradient(135deg, hsl(200, 60%, 85%), hsl(340, 70%, 85%));
      height: 100vh;
      display: flex;
      flex-direction: column;
    }

    /* Header */
    .header {
      height: 60px;
      background: rgba(255, 255, 255, 0.9);
      backdrop-filter: blur(10px);
      border-bottom: 1px solid rgba(0, 0, 0, 0.1);
      display: flex;
      align-items: center;
      justify-content: space-between;
      padding: 0 20px;
      box-shadow: 0 4px 10px rgba(0, 0, 0, 0.1);
    }

    .header .logo {
      font-size: 20px;
      font-weight: bold;
      color: #333;
    }

    .header .user-avatar {
      width: 40px;
      height: 40px;
      border-radius: 50%;
      background: url('https://via.placeholder.com/40') no-repeat center/cover;
      border: 2px solid #fff;
      box-shadow: 0 4px 10px rgba(0, 0, 0, 0.2);
    }

    /* Main Container */
    .main-container {
      display: flex;
      flex: 1;
      overflow: hidden;
    }

    /* Sidebar */
    .sidebar {
      width: 250px;
      background: rgba(255, 255, 255, 0.9);
      backdrop-filter: blur(10px);
      border-right: 1px solid rgba(0, 0, 0, 0.1);
      display: flex;
      flex-direction: column;
      padding: 20px;
      box-shadow: 2px 0 10px rgba(0, 0, 0, 0.1);
    }

    .sidebar ul {
      list-style: none;
    }

    .sidebar ul li {
      margin-bottom: 15px;
      cursor: pointer;
      padding: 10px;
      border-radius: 5px;
      transition: background 0.3s ease;
    }

    .sidebar ul li:hover {
      background: rgba(0, 0, 0, 0.1);
    }

    /* Content */
    .content {
      flex: 1;
      padding: 20px;
      overflow-y: auto;
      background: rgba(255, 255, 255, 0.8);
      backdrop-filter: blur(10px);
    }
  </style>
</head>
<body>
  <!-- Header -->
  <div class="header">
    <div class="logo">LOGO</div>
    <div class="user-avatar"></div>
  </div>

  <!-- Main Container -->
  <div class="main-container">
    <!-- Sidebar -->
    <div class="sidebar">
      <ul>
        <li>仪表盘</li>
        <li>用户管理</li>
        <li>设置</li>
        <li>退出登录</li>
      </ul>
    </div>

    <!-- Content -->
    <div class="content">
      <h1>欢迎来到内容区域</h1>
      <p>这里是主要内容区域，您可以在这里显示动态数据、图表或其他内容。</p>
    </div>
  </div>
</body>
</html>
